An image display device which is fixed to a head or a face of a user who observes an image, that is, a head mounted display, is known. The head mounted display includes, for example, image display units for respective left and right eyes, and is configured to be used together with headphones so as to be capable of controlling visual and auditory senses. When the head mounted display is configured to completely shut out the outside world while being mounted on the head, virtual reality during viewing and listening is enhanced. The head mounted display also enables different videos to be projected on the left and right eyes. Therefore, when images with parallax are displayed for the left and right eyes, a 3D image can be presented.
This kind of head mounted display causes virtual images to be formed on retinas of the eyes and be observed by the user. The virtual image as used herein is formed on an object side of a lens when the object is located at a position close to the lens within a focal length. For example, a head mounted display has been proposed which is configured such that an optical system with a wide viewing angle is arranged in front of pupils at an interval of 25 mm, and a display panel having a size of an effective pixel range of about 0.7 in is further arranged in front of the optical system with the wide viewing angle (for example, refer to Patent Document 1).
By using this kind of head mounted display, a wide angle image can be viewed. For example, a head mounted display has been proposed which is configured such that a head motion tracking device including a gyro sensor or the like is attached to a head so as to allow a user to feel a 360-degree video of a whole space following a movement of the head of the user (for example, refer to Patent Document 2 and Patent Document 3). A displayed region is moved so that the movement of the head detected by the gyro sensor is canceled, whereby the user is allowed to observe an image following the movement of the head of the user and look over the whole space.
It is preferable that the head mounted display presents an image following the movement of the motion of the head of the user with a shorter delay time. A sense of feeling that the image is following the motion of the head is deteriorated by a long delay time. In addition, it is concerned that the user may feel sick.